The present invention relates to a power steering system, and more particularly to a power steering system driven by an electric motor.
Known motor-driven power steering systems are composed of an electric motor for applying assistive power to the linkage of the power steering system to assist in steering operation, a power supply for energizing the electric motor, a detector for detecting the steering torque imposed on the steering wheel and generating a signal representative of the detected steering torque, and a control circuit responsive to the output signal from the detector for controlling the current supplied from the power supply to the motor.
Such conventional motor-driven power steering systems are disclosed in Japanese Laid-Open Utility Model Publication No. 59-68234 and Japanese Laid Open Patent Publication No. 59-50864 (corresponding to U.S. patent application Ser. No. 405,705 filed Aug. 5, 1982), for example. In these prior motor-driven power steering systems, the motor is located near the steering shaft connected to the steering wheel (Japanese Laid-Open Utility Model Publication No. 59-68234), or the motor is disposed directly on the shaft which transmits the rotational torque (Japanese Laid-Open Patent Publication No. 59-50864).
With the above conventional arrangements, however, vibration produced where the motor is energized tends to be transmitted directly to the steering wheel, or noise caused by the motor is apt to enter the passenger compartment of the automobile.